The present invention relates to a system for gas turbine engines, and more particularly to an oil scavenge system therefore.
Gas turbine engines employ high-speed bearings that require a continuous supply of oil for lubrication and cooling. For optimum performance, the oil flow must be properly directed to and from the bearings. Failure to remove or scavenge oil from the bearing may be as detrimental to the bearing as insufficient oil flow because the churning of unscavenged oil within the bearing may also lead to overheating.
In a conventional lubrication system, oil is supplied to the rolling elements of the bearings under pressure. Then gravity, compartment pressurization or its dynamics is relied upon to drain back to a sump. One effective way to accomplish the return flow is to maintain an open, conical, and unrestricted passageway from the bearing back to the sump.
An engine that uses a high speed turbine, such as a geared turbofan engine, requires a relatively large disk bore for structural integrity. A sealed bearing compartment separates oil from the hot external environment air which is in close proximity to a heated turbine disk bore. As engine core size constraints become more aggressive and speeds increase, disadvantages of conventional scavenger systems may occur. If, for example, the engine length is reduced, the bearing compartment may be closely fitted inside the disk bore. In particular, as the size of the sump region decreases, the distance between the compartment seals and the free surface of collected oil decreases. This often results in a long and narrow bearing compartment.
During level attitude operation, the oil is supplied to the bearing, then collects at the bottom and rear of the bearing compartment where the oil is scavenged by a pump for filtration and re-use. During nose down attitudes, however, such as those required for aircraft descent, a long and narrow bearing compartment shape may create a dam that will prevent oil in the front of the compartment from being effectively scavenged such that adjacent seals may become flooded (FIG. 7). Compartment seals may leak under such a flooded condition and the oil may over time eventually pool in the hot external environment and may become problematic.
Accordingly, it is desirable to provide an oil scavenge system for a long and narrow bearing compartment shape to minimize or prevent oil leakage during all operating conditions.